AW: Re: aliasing again

From Haible_Juergen#Tel2743
Sent Sat, Oct 19th 1996, 03:01

> When you do a DAC thing you will have the spectrum being folded up several
> times. So to suppress the mirror waveforms you _will_ need an filter on 
the
> output.
[...]
>So the mirrors needs to be cut out by a rather steep low pass filter.

Yes, you're right. Good description btw.!

My original point was that you can't prevent aliasing with a filter after
the dac (i.e. if the mirrored spectra already overlap, you're lost).
Just forgot that you still have to filter the mirrors out, not just the
clock, in the general case - sorry.

What I had in mind was a special case, when the playback clock is
some HF-VCO, which directly reads out the date from a ram.
I think the sample module of the old doepfer modular
worked this way, and some drum machines. This approach should
make the spectral lines of the mirrors harmonics of the original as well.
Lack of filter just makes the sound brighter, but not unharmonic.

Does anybody know which sample machines actually worked like
this?

JH.